The present invention relates to industrial processing plants. More particularly, the present invention relates to pressure transmitters used to measure pressure in such plants.
Pressure transmitters are typically assembled in a clean, controlled factory or workbench environment by fitting a pressure sensor module and a converter module together. Each of the two modules includes a housing with a threaded joint where electronic circuitry is exposed and accessible for connection to the other module. The two threaded joints are threaded together, and each module is sealed off by its connection to the other module to form the finished pressure transmitter and protect the internal electronic circuits.
Before the modules are joined, however, exposed electronic parts in the sensor modules can be damaged by handling, spilled or airborne corrosive chemicals, or weather conditions. These damaging conditions are often present in an installation location such as a chemical processing plant. Pressure transmitters are thus usually pre-assembled before they are brought into a process plant environment. This also means that the converter modules have to be completed before the sensor module is installed on the process piping. It has been found that in many instances it is desirable to install the pressure sensor module onto the process piping and pressurize the system before the plant is completed, and before the converter design is selected. Thus, a pressure sensor module that protects the electronic parts before a converter module is installed is desired.
A pressure sensor module comprises a hermetically sealed housing or external support structure that is integrally formed and surrounds and encloses a pressure sensor and a circuit for the sensor. The housing has a threaded process fluid inlet and a threaded sleeve adapted to support a converter module. The sleeve also supports a feedthrough that is adapted to couple electrical contacts to the converter module.
The isolator is adapted to receive process fluid and couples to the pressure sensor, forming a transducer in the pressure converter. The circuit in the pressure sensor module couples to the pressure sensor and provides a bus for energization, control, and a digital representation of pressure. The feedthrough has contacts or pins that couple to the lines of the bus, and has an insulator barrier wall surrounding the contacts.
The housing is preferably sealed to both the isolator and the feedthrough in a manner that prevents access to the pressure sensor and circuit using ordinary tools. The pressure sensor module can be safely handled, installed and remain in a process plant installation environment where it is subject to rough handling, chemical spills and vapors without having a converter installed thereon and without exposing electronic parts of the sensor module to the environment.